The present invention relates to cooling fans such as fans used in connection with an automotive or industrial cooling system. More specifically, the invention pertains to fans with integral blades formed in a molding process, such as an injection molding procedure.
Most automotive and industrial power components require some form of auxiliary cooling system. In a typical automotive application, this cooling system includes a radiator and a cooling fan that directs air across the radiator. In these applications, the fan is mounted to a rotating flange of a fan drive that is separate from the power plant output.
In the early design of such cooling fans, metal blades were mounted to a metal hub, which hub was then attached to the fan drive. In recent years, however, high-strength polymer materials have been used to form various components of the fan. The polymer fan design was found to be capable of withstanding the normal forces and stresses endured by a cooling fan in even the heaviest duty automotive or industrial application. Moreover, the use of polymer materials provided a significant reduction in weight of the cooling fan. Moreover, and perhaps most significantly, the use of polymers generated significant benefits in the manufacture of the fan, since materials of this type readily lend themselves to a variety of molding processes.
The one-piece molded fan has eliminated the welds and rivets commonly associated with prior metal fans. In addition, the molding process facilitated the generation of smooth rounded contours, which ultimately reduced internal stresses within the fan structure.
In one type of molded fan design, the entire fan and hub are formed in a single piece. An example of this form of a one-piece molded fan is shown in U.S. Pat. No. 4,671,739 to Read et al. Fans of this type were found to be better suited for smaller duty applications, such as for use in the cooling system of passenger automobiles. For larger, higher stress applications, a hubless molded fan design was found to be more appropriate. One such design is depicted in U.S. Pat. No. 5,593,283 to Scott. In this design, a polymer hubless fan is integrally formed around a metallic mounting hub. This mounting hub can be supported within the molding apparatus, such as a typical injection molding machine. The polymer material is then injected into a mold surrounding the hub to form an interlocking ring around the metal hub.
In many automotive and industrial applications the molded fan includes a polymer, such as polypropylene, nylon or other resin compositions. In addition, many industrial fans include reinforcing material such as glass fibers or nylon strands. The reinforcing material can be oriented within the structure of the molded fan blade to provide additional strength and stiffness where needed based upon stress analysis of the working fan.
The hubless fan design has evolved since its inception. While the metal mounting hub provides a certain degree of strength to the overall fan, the molded fan can include an enlarged polymer ring formed around the mounting hub. This ring helps provides strength and bending or flexure stiffness to the root of each of the fan blades.
While the hubless polymer fan represents an improvement over prior metal and one-piece polymer fan constructions, improvements are still needed. For instance, cost and material considerations are implicated by current molded fan designs involving significant material waste. Cost considerations are also involved in the storing and shipping of an inventory of fans. There remains a need for a molded fan assembly that reduces the overall costs associated with manufacturing and shipping the final fan product.